/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.library.frequency;

import org.apache.iotdb.library.util.Util;
import org.apache.iotdb.udf.api.UDTF;
import org.apache.iotdb.udf.api.access.Row;
import org.apache.iotdb.udf.api.collector.PointCollector;
import org.apache.iotdb.udf.api.customizer.config.UDTFConfigurations;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameterValidator;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameters;
import org.apache.iotdb.udf.api.customizer.strategy.RowByRowAccessStrategy;
import org.apache.iotdb.udf.api.type.Type;
import org.eclipse.collections.impl.list.mutable.primitive.DoubleArrayList;
import org.eclipse.collections.impl.list.mutable.primitive.IntArrayList;
import org.jtransforms.fft.DoubleFFT_1D;

import java.text.SimpleDateFormat;

/**
 * This function does Inverse Fast Fourier Transform for input series.
 */
public class UDTFIFFT implements UDTF {

    private final DoubleArrayList real = new DoubleArrayList();
    private final DoubleArrayList imag = new DoubleArrayList();
    private final IntArrayList time = new IntArrayList();
    private long start;
    private long interval;

    @Override
    public void validate(UDFParameterValidator validator) throws Exception {
        validator
                .validateInputSeriesNumber(2)
                .validateInputSeriesDataType(0, Type.DOUBLE, Type.FLOAT, Type.INT32, Type.INT64)
                .validate(
                        x -> (long) x > 0,
                        "interval should be a time period whose unit is ms, s, m, h, d.",
                        Util.parseTime(validator.getParameters().getStringOrDefault("interval", "1s")));
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        if (validator.getParameters().hasAttribute("start")) {
            validator.validate(
                    x -> (long) x > 0,
                    "start should conform to the format yyyy-MM-dd HH:mm:ss.",
                    format.parse(validator.getParameters().getString("start")).getTime());
        }
    }

    @Override
    public void beforeStart(UDFParameters parameters, UDTFConfigurations configurations)
            throws Exception {
        configurations.setAccessStrategy(new RowByRowAccessStrategy()).setOutputDataType(Type.DOUBLE);
        this.interval = Util.parseTime(parameters.getStringOrDefault("interval", "1s"));
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        this.start = 0;
        if (parameters.hasAttribute("start")) {
            this.start = format.parse(parameters.getString("start")).getTime();
        }
    }

    @Override
    public void transform(Row row, PointCollector collector) throws Exception {
        if (!row.isNull(0)
                && !row.isNull(1)
                && Double.isFinite(Util.getValueAsDouble(row, 0))
                && Double.isFinite(Util.getValueAsDouble(row, 1))) {
            time.add((int) row.getTime());
            real.add(Util.getValueAsDouble(row, 0));
            imag.add(Util.getValueAsDouble(row, 1));
        }
    }

    @Override
    public void terminate(PointCollector collector) throws Exception {
        int n = time.get(time.size() - 1) + 1;
        double a[] = new double[n * 2];
        for (int i = 0; i < time.size(); i++) {
            int k = time.get(i);
            a[k * 2] = real.get(i);
            a[k * 2 + 1] = imag.get(i);
            // conjugate
            if (k > 0) {
                k = n - k;
                a[k * 2] = real.get(i);
                a[k * 2 + 1] = -imag.get(i);
            }
        }
        DoubleFFT_1D fft = new DoubleFFT_1D(n);
        fft.complexInverse(a, true);
        for (int i = 0; i < n; i++) {
            collector.putDouble(start + i * interval, a[2 * i]);
        }
    }
}
